Spinning head with an exchangeable, self-sealing nozzle assembly

ABSTRACT

A spinning head for the melt spinning of thermoplastic polymers, with a nozzle assembly which is withdrawable and insertable from the service end of the spinning head in drawer-like fashion, and is designed for self-sealing under the action of the melt pressure. The nozzle assembly is releasably connected to the stationary melt-supplying member with the aid of longitudinally extending cooperating guideways on this feed member and on the casing of the nozzle assembly, respectively, and these guideways are so disposed that the melt pressure sets up substantially only tensional stresses in the melt casing. This design makes it possible to reduce the thickness of the casing, and it is easier to gain access into the nozzle assembly for inspection and cleaning.

United States Patent [191 Lenk [ June 24, 1975 [75] Inventor: ErichLenk, Remscheid, Germany [73] Assignee: Barmag Barmer MaschinenfabrikAktiengesellschaft, Wuppertal, Germany 22 Filed: Sept. 27, 1973 21 Appl.No.: 401,540

[30] Foreign Application Priority Data Yamada et a1 425/192 X Kilsdonk425/464 X Primary Examiner-Andrew R. Juhasz Assistant ExaminerZ. R.Bilinsky Attorney, Agent, or F irm-Johnston, Keil, Thompson & ShurtleffABSTRACT A spinning head for the melt spinning of thermoplasticpolymers, with a nozzle assembly which is withdrawable and insertablefrom the service end of the spinning head in drawer-like fashion, and isdesigned for self-sealing under the action of "the melt pressure. Thenozzle assembly is releasably connected to the stationary melt-supplyingmember with the aid of longitudinally extending cooperating guideways onthis feed member and on the casing of the nozzle assembly, respectively, and these guideways are so disposed that the melt pressuresets up substantially only tensional stresses in the melt casing. Thisdesign makes it possible to reduce the thickness of the casing, and itis easier to gain access into the nozzle assembly for inspection andcleaning.

10 Claims, 6 Drawing Figures PATENTEUJUN 24 ms SHEET FIG. I

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3 8 91, 379 PAIENTED JUN 24 I975 SHEET 2 SPINNING HEAD WITH ANEXCHANGEABLE, SELF-SEALING NOZZLE ASSEMBLY The invention relates tospinning heads for the spinning of thermoplastic polymers, and moreparticularly to such spinning heads which permit easy removal of thenozzle assembly proper for the purpose of cleaning or replacement. Theinvention also relates to multi-unit spinning head apparatus of thisgeneral kind.

Spinning heads are known wherein the nozzle assembly may be withdrawnand inserted in an axial direc tion, usually from the lower end of thespinning head. Representative of this hanging type of construction areGerman published patent application No. 1,660,375 and German Pat. No.1,246,221, for example. In these known spinning heads clamping means inthe form of vertically extending bolts or threaded clamping rings areprovided by which the nozzle assembly is pressed upwardly against themember through which the melt is supplied to the top of the nozzleassembly. The pressure thus mechanically exerted on the various sealswhich keep the melt from leaking to the outside of the nozzle assemblyis supplemented by the melt pressure itself which in these designs tendsto urge the different parts of the nozzle assembly away from each otherand against the seals. In the case of German Pat. No. 1,246,221 theseparts include an annular piston designed to step up the pressure appliedby the melt to the principal seal.

Spinning heads of this known construction have the disadvantage thatvertical space must be set aside underneath the spinning head for theremoval of the nozzle assembly. Also, since in arrangements of this kindthe spinning chute is typically located in this general dismountingarea, the chute interferes with the withdrawal and insertion operationand must be made of movable design. In the case of multi-unit spinninghead apparatus, moreover, it becomes impossible during the exchange ofone of the nozzle assemblies to continue operation with one of the othernozzle assemblies. In addition, the forces involved in sealing thenozzle assembly and securing it to the stationary feed member are largeand their distribution is disadvantageous so that the resulting designis relatively bulky.

Spinning heads have been proposed in which the above mentioneddisadvantage of lost space under neath the nozzle assembly is avoided bymaking this assembly removable in a lateral direction, i.e., in adirection generally perpendicular to the axis of the spinning head. Inthese arrangements the stationary feed memher at its lower extremity isgenerally in the shape of a C which is open towards the service side ofthe spinning head. The bottom leg of this C forms a ledge by which thenozzle assembly is supported and on which the nozzle assembly can bemoved outwardly or inwardly in drawer-like fashion.

In German published patent application No. 1,276,861 the foregoingconstruction is implemented by means of wedges which are supported bythe afore mentioned bottom leg of the C-shaped stationary member andwhich cooperate with inclined, downwardly facing surfaces on the nozzleassembly. The wedges can be drawn against the rear wall of the C bymeans of bolts and, as a result, the nozzle assembly is pressed againsta seal at its top, thereby to seal the nozzle assembly at the point ofmelt supply.

In my own German published patent application No. 1,529,819 self-sealingis used, i.e., the sealing of the nozzle assembly is effected under theaction of the melt pressure, with preloading by resilient meansinterposed between the die plate and a piston which is axially movableand carries a seal at least at its upper end.

While my last-mentioned design in other respects is satisfactory, thisdesign, as well as that according to the above German application Pat.No. 1,276,861, suffers from the drawback that the relatively largeforces exerted on the C shaped portion of the stationary member subjectthis portion to bending stresses and tend to spread the two legs of theC apart. As a consequence this portion, and particularly the bottom legof the C, must be made relatively thick and this renders the designrather voluminous and heavy. These larger dimensions, in turn, adverselyaffect the visibility of the nozzle assembly from the service side ofthe spinning head and also detract from the accessibility of the nozzleassembly in cleaning operations.

It is an object of the invention to provide a spinning head exhibitingthe advantages of the known designs without being subject to theirdisadvantages.

More particularly, it is an object of the invention to provide aspinning head in which the nozzle assembly is connected to themelt-supplying member in a way affording desirable distribution offorces, and so that these forces are transmitted to the melt-supplyingmember directly; that the advantageous drawer-type design is retained;and that, in the instance of a multiunit spinning head apparatus, if oneof the nozzle assemblies is being exchanged, spinning may be continuedwith an adjacent nozzle assembly.

According to the principle aspect of the invention the foregoing objectsare obtained, briefly, by providing on the stationary feed member and onthe casing member forming the holding element of the nozzle assembly,elongated cooperating guideways formed for instance by guide bars ofgenerally rectangular cross section so that this casing with thespinning elements therein may be laterally withdrawn from and insertedin the spinning head. The aforementioned guideways are disposed so thatthe self-sealing forces which are due to the action of the melt pressuresubstantially set up, in a direction parallel to the axis of thespinning head, merely tensional stresses in the above casing.Preferably, one of the two members thus releasably secured together hasformed therein adjacent its guide bars, guide grooves in which the guidebars of the other member slide. The mating faces of the guideways may beplane or they may be of dove-tail design. In addition to theaforementioned spinning elements say a die plate and a filter the casingmay also contain a piston with a passage therein for the melt and aresilient or deformable sealing element such as an annular diaphragmcooperating with the piston to facilitate self-sealing under the actionof the melt pressure.

In the design according to the invention the nozzle assembly can bemoved from the service side of the spinning head in drawer'like fashion,and because of this transverse direction of movement of the nozzleassembly, the latter can be exchanged simply and quickly. The meltpressure is utilized both for selfsealing and for providing the clampingforces between the nozzle assembly and the feed member carrying thisassembly, effective directly by way of the aforementioned guideways. Inthis fashion a force distribution is obtained which involves loops oflines of force closed over the cooperating parts of the guideways, thelengthwise extent of the casing. and a support provided adjacent itslower end. Because of the tensional nature of the stresses set up in thecasing only thin walls are required for the latter, thereby reducing thespace occupied by the casing.

By virtue of this design the dimensions of the spinning head itself canbe similarly reduced and this in turn reduces the space requirements ofthe heat box surrounding it. Also, because of the reduced dimensions ofthe casing of the nozzle assembly, visibility of the spinning assemblyfrom the service side and accessibility in cleaning its parts aregreatly enhanced.

A design of comparable merits is obtained by the use of the principlesof the invention if the piston with its bore, which is provided tofacilitate self-sealing, is mounted along with the diaphragm element asa part of the feed member carrying the nozzle assembly, rather than as apart of the nozzle assembly itself.

According to another feature of the invention the plurality of nozzleassemblies disposed one behind the other in the direction of insertionmay be associated with a common member carrying them, in drawer-likefashion, by means of guideways of the kind mentioned.

According to yet another feature of the invention a plurality of nozzleassemblies disposed side by side with respect to the direction ofinsertion may be so associated with a common carrying member.

These multi-unit arrangements result in compact designs which mayadvantageously include a single heat box surrounding the entire spinninghead assembly.

Illustrated embodiments of the invention will now be described withreference to the accompanying drawings, in which:

FIG. 1 is a part-sectional front view of a spinning head according tothe invention, including meltsupplying member, metering pump, heat box,and an exchangeable nozzle assembly;

FIG. 2 schematically illustrates a multi-unit spinning head apparatusaccording to the invention in which a plurality of nozzle assemblies arearranged side by side;

FIG. 3 schematically illustrates a multi-unit spinning head apparatusaccording to the invention in which a plurality of nozzle assemblies arearranged one behind the other; and

FIG. 4 is a plan view of a casing, taken by itself, of the nozzleassembly of the spinning head as in FIG. 1.

FIGS. 5 and 6 are sectional front views of two other alternativeembodiments of the invention.

Referring now to FIG. 1, the spinning head illustrated in this figuresubstantially comprises a stationary feed member 2 having a verticalpassage 25 therein through which the melt is fed under the control ofmetering pump 17. Reference numeral 9 denotes the side walls of a heatbox enclosing the spinning head.

Feed member 2 carries a nozzle assembly 1 having a generallycube-shaped, thin-walled retaining or casing member 3 shown in plan viewin FIG. 4. As will be seen from the two figures, casing 3 has acylindrical cavity or well 19 therein which is open at the front andrear as viewed in FIG. 1, and also has a cylindrical meltdischargeopening 20 at the bottom, which is defined by the inner wall ofsupporting flange 10 of easing 3. Stacked within cylindrical cavity 19of easing 3 are spinning elements including a cylindrical die plate 4having spinning orflces or nozzles 21 therein, a likewise cylindricalfilter element 8 associated with this die plate. and a cylindricalpiston 5 having a central bore 22 aligned with feed member passage 25.Abutting the bottom face of the piston, in sealing or connectedrelationship such by heat deformation or by welding, is a disc-shapedmetallic member or diaphragm 6 which is similarly sealed at itsperiphery to that of filter 8. Diaphragm 6 has a central aperturetherethrough. On its top side piston 5 is provided with a gasket orsealing means 7 designed to form a seal with respect to the bottom faceofa lower extension 23 of feed member 2. Another gasket 7 is preferablyinserted between flange l0 and plate 4.

This extension 23 has a depth that is a front-torear extent not visiblein FIG. 1 which corresponds to that of easing 3, and it has the shape ofan inverted T. The horizontal legs 24, 24' of this T are of rectangularcross section and form ledges or guide bars for the sliding movement ofthe nozzle assembly in the withdrawal and insertion of the latter, andthey leave above them corresponding rectangular guide grooves 12 and 12which mate, respectively, with inwardly extending guide bars 11 and 11of rectangular cross section which are formed at the top end of casing3. The guide bars l1, l1 and 24, 24' form guideways which serve tomechanically couple nozzle assembly 1 to feed member 2 in the operatingcondition of the spinning head while, at the same time, affording meansfor the withdrawal of nozzle assembly 1 from and its insertion into thespinning head from the service end (the front end of FIG. 1) of thespinning head in a direction normal to the axis of the latter indrawer-like fashion. As will be appreciated from FIGS. 1 and 4, once thenozzle assembly has been withdrawn, die plate 4, filter 8 and piston 5with diaphragm 6 and sealing means 7, can be removed from casing 3 fromthe top end thereof for inspection, repair or replacement. Similarly,casing 3 is originally loaded, or is reloaded, with these parts from thetop.

In the operation of the spinning head the pressure of the melt suppliedthrough passage 25 and bore 22, through the medium of filter 8 urges dieplate 4 against support flange 10 of casing 3 and, on the other hand,urges axially movable piston 5 with its sealing element 7 against thebottom face of extension 23 of stationary feed member 2; diaphragm 6expands or is deformed in the process. In this fashion the melt pressurefunctions to provide an auotmatic seal both with respect to feed member2 and casing member 3. At the same time the melt pressure operates tosecurely connect the nozzle assembly mechanically to the feed memberand, in doing so, acts via legs or guide bars 24, 24' and l1, l1, andvia flange 10 at the bottom end of easing 3, to set up in the wall ofthis casing substantially only tnesional stresses which extend in adirection parallel to the axis of the spinning head.

Feed member 2 and nozzle assembly I are thus locked together under theaction of the melt pressure, by loops of lines of force which are closedover the aforementioned guideways, the axial or lengthwise extent ofcasing 3, and flange 10 in series. It is due to the tensional characterof the stresses in casing 3 that its dimensions can be held to aminimum, and this in turn results in the improved properties of thedesign according to the invention from the standpoint of visibility andaccessibility of the nozzle assembly. Also, no space for the dismountingof the nozzle assembly is lost therebelow.

FIG. 2 shows a multi-unit spinning head in which a plurality of nozzleassemblies the four assemblies, 13a, 13b, 13c, 13d in the exampleillustrated are carried and served by a common stationary feed member 14having a corresponding number of melt passages (not shown). This commonmember is enclosed by a heat box 9'. As indicated in FIG. 2, the nozzleassemblies are designed in particular, connected to the feed member andsealed in a manner explained above in conjunction with FIGS. 1 and 4.The four nozzle assemblies are mounted in side-by-side relationship,that is, they are aligned in a direction perpendicular to that ofwithdrawal and insertion of the assemblies.

FIG. 3 illustrates a multi-unit spinning head in which a number ofnozzle assemblies a, 15b, 15c, are similarly carried and served by acommon stationary feed member 16. Again, the design of the nozzleassemblies and their connection to the feed member corresponds to thetechnique described hereinabove with respect to FIGS. 1 and 4. Thenozzle assemblies are aligned in this embodiment one behind the other,that is, in a direction parallel to the direction of withdrawal andinsertion of the assemblies. This arrangement lends itself forinstallations in which two or three assemblies are to be so placed withrespect to each other.

The arrangements of FIGS. 2 and 3 make it possible to provide a largenumber of easily and quickly replaceable nozzle assemblies in arelatively limited space. Self-sealing and secure mounting take placeunder the action of the melt pressure and the assemblies can be easilyobserved and cleaned from the service side, all as previously explained.

As indicated above, instead of providing the piston with its diaphragm,in the casing of the nozzle assembly, it is also possible to slidablymount the piston in the stationary feed member. Also, while thecooperating guide bars on the two members have been shown with planemating faces, it is also possible to provide the cooperating guide barswith dove-tail shaped work surfaces instead.

Referring to the embodiments shown in FIGS. 5 and 6, the feed member 2ahas an enlarged bore at the end of the vertical feed passage 25a toreceive a cylindrical piston 5a and the diaphragm 6a which cooperateunder the influence of the melt pressure to produce a tight seal withthe nozzle assembly over the annular gasket or sealing element 7a. Thepiston and diaphragm combination is supported by the spring retentionring 28 which may also be used to prestress or place an initial tensionon the sealing element 7a before the melt is introduced.

In all embodiments of the invention, the diaphragm 6 or 6a may becomposed of a resilient metal such as a corrosion-resistant steel alloywhich may be welded to the piston along an inner edge or surface suchthat there is a resilient or elastic displacement of the diaphragm undermelt pressure and an ability to spring back when this melt pressure isrelieved. It is especially advantageous, however, to employ a diaphragmwhich is a deeply drawn sealing element composed of aluminum, and whichis simply inserted into its correct position during assembly of thespinning unit. Under high melt pressure and temperature, this aluminumdisc or diaphragm undergoes deformation so as to be applied in a tightand close fitting relationship with the abutting wall members. Such analuminum sealing element then serves as a simple throwaway gasket whichis replaced during each reassembly of the spinning head. Because of thehigh viscosity of the melt, it is practically impossible for any leaksto occur in the self-sealing arrangement. Also, such a deformable gasketor seal offers a large area of surface contact with the melt to transmitpressure to the relatively smaller annular surface are of the sealingmeans 7 or 7a.

In FIG. 5, the nozzle plate 4 with filter pack 8 is fixed in placewithin the casing 3a by the pressure exerted through the threading 20 ofthe cover member 26 having a cylindrical shape and being sealed againstthe nozzle plate 4 by the annular gasket 27. Key holes. slots 29 or thelike, can be provided in the upper face of cover member 26 to permit theinsertion of a tool in tightening or loosening this threaded member.

In FIG. 6, the nozzle plate 4 with filter 8 is directly secured to thecasing 26 which is integral with the covering means above the nozzleassembly, i.e., so as to provide a unitary casing and nozzle assemblysimilar to FIG. 6. One advantage of these alternative embodimentsresides in the reinforcement of the casing 3 or 26 by joining the nozzleplate 4 and/or the covering means 26 or 26 to each other. Members lla orIla still cooperate with the grooved portion 12 of the feed member 2a topermit the sliding insertion or removal of the casing and nozzleassembly laterally of the feed member. Moreover, sealing or clampingforces and tensions in the lower drawer-like structure, as exerted bythe melt pressure, still extend substantially only in an axial directionwithout any tendency to damage or distort the self-sealing structure.This additional strengthening of the withdrawable nozzle and casingunits does not prevent a rapid interchange of such units, although theydo require some additional time for complete disassembly or reassemblyof their component parts. On the other hand, the embodiment of FIG. 6has the further advantage that it can have a nozzle plate in the form ofa rectangular die or so--called line die". These and similar alternativeconstructions within the scope of the invention will be readilyunderstood by those skilled in this art.

This invention is hereby claimed as follows:

1. A spinning head for the spinning of thermoplastic polymers around avertical axis, including a relatively stationary feed member supplyingthe melt, a nozzle assembly laterally withdrawable from and insertablein said spinning head and connectable to said feed member inself-sealing relationship under the action of the melt pressure, saidnozzle assembly comprising a casing member and, supported by andretained in said casing member, spinning elements including at least adie plate, elongated cooperating guideways being respectively providedon said feed member and said casing member for the withdrawal andinsertion of said casing member with said spinning elements therein,said guideways being disposed so that the self-sealing forces due to theaction of the melt pressure give rise, in a direction parallel to thevertical axis of said spinning head, substantially to only tensionalstresses in said casing member.

2. A spinning head as claimed in claim 1, wherein said casing memberadjacent its lower end has an inwardly extending support portion againstwhich said die plate bears when subjected to said melt pressure.

3. A spinning head as claimed in claim 2, wherein said guidewayscomprise cooperating guide bars on said two members, respectively, saidcooperating guide 7 bars being urged by said melt pressure against eachother, and one of said members having formed therein adjacent its guidebars, guide grooves in which the guide bars of the other member ride.

4. A spinning head as claimed in claim 1, wherein said spinning headfurther includes a piston containing a bore aligned with a passage insaid feed member.

5. A spinning head as claimed in claim 4, wherein said spinning headalso includes sealing means interposed between said piston on the onehand and a filter associated with said die plate on the other hand.

6. A spinning head as claimed in claim 5, wherein said piston and saidsealing means are part of said nozzle assembly, said piston beingmounted for slidable movement in said casing member.

7. A spinning head as claimed in claim 5, wherein said piston and saidsealing means are mounted in said feed member.

8. A multi-unit spinning head apparatus having a plurality of nozzleassemblies, said appratus including a relatively stationary feed membercommon to said nozzle assemblies for supplying the melt to theindividual assemblies, each said nozzle assembly being laterallywithdrawable from and insertable in said feed member and eonnectable tosaid member in self-sealing relationship under the action of the meltpressure, and each comprising a casing member and, supported by andretained in said casing member, spinning elements including at least adie plate, and said apparatus further including a plurality of elongatedcooperating guideways respectively provided on said common feed memberand on the individual casing members, for the withdrawal and insertionof any of said casing members with the corresponding elements therein,each of said plurality of cooperating guideways being disposed so thatthe self-sealing forces due to the action of the melt pressure giverise, in a direction parallel to the axis of the corresponding nozzleassembly, substantially to only tensional stresses in the respectivecasing member.

9. A multi-unit spinning head appratus as claimed in claim 8, whereinsaid plurality of nozzle assemblies are mutually aligned in a directionnormal to the direction of withdrawal and insertion of said assemblies.

10. A multi-unit spinning head apparatus as claimed in claim 8, whereinsaid plurality of nozzle assemblies are mutually aligned in a directionparallel to the direction of withdrawal and insertion of saidassemblies.

l l l l

1. A spinning head for the spinning of thermoplastic polymers around avertical axis, including a relatively stationary feed member supplyingthe melt, a nozzle assembly laterally withdrawable from and insertablein said spinning head and connectable to said feed member inself-sealing relationship under the action of the melt pressure, saidnozzle assembly comprising a casing member and, supported by andretained in said casing member, spinning elements including at least adie plate, elongated cooperating guideways being respectively providedon said feed member and said casing member for the withdrawal andinsertion of said casing member with said spinning elements therein,said guideways being disposed so that the self-sealing forces due to theaction of the melt pressure give rise, in a direction parallel to thevertical axis of said spinning head, substantially to only tensionalstresses in said casing member.
 2. A spinning head as claimed in claim1, wherein said casing member adjacent its lower end has an inwardlyextending support portion against which said die plate bears whensubjected to said melt pressure.
 3. A spinning head as claimed in claim2, wherein said guideways comprise cooperating guide bars on said twomembers, respectively, said cooperating guide bars being urged by saidmelt pressure against each other, and one of said members having formedtherein adjacent its guide bars, guide grooves in which the guide barsof the other member ride.
 4. A spinning head as claimed in claim 1,wherein said spinning head further includes a piston containing a borealigned with a passage in said feed member.
 5. A spinning head asclaimed in claim 4, wherein said spinning head also includes sealingmeans interposed between said piston on the one hand and a filterassociated with said die plate on the other hand.
 6. A spinning head asclaimed in claim 5, wherein said piston and said sealing means are partof said nozzle assembly, said piston being mounted for slidable movementin said casing member.
 7. A spinning head as claimed in claim 5, whereinsaid piston and said sealing means are mounted in said feed member.
 8. Amulti-unit spinning head apparatus having a plurality of nozzleassemblies, said appratus including a relatively stationary feed membercommon to said nozzle assemblies for supplying the melt to theindividual assemblies, each said nozzle assembly being laterallywithdrawable from and insertable in said feed member and connectable tosaid member in self-sealing relationship under the action of the meltpressure, and each comprising a casing member and, supported by andretained in said casing member, spinning elements including at least adie plate, and said apparatus further including a plurality of elongatedcooperating guideways respectively provided on said common feed memberand on the individual casing members, for the withdrawal and insertionof any of said casing members with the corresponding elements therein,each of said plurality of cooperating guideways being disposed so thatthe self-sealing forces due to the action of the melt pressure giverise, in a direction parallel to the axis of the corresponding nozzleassembly, substantially to only tensional stresses in the respectivecasing member.
 9. A multi-unit spinning head appratus as claimed inclaim 8, wherein said plurality of nozzle assemblies are mutuallyaligned in a direction normal to the direction of withdrawal andinsertion of said assemblies.
 10. A multi-unit spinning head apparatusas claimed in claim 8, wherein said plurality of nozzle assemblies aremutually aligned in a direction parallel to the direction of withdrawaland insertion of said assemblies.